This project investigates the neural mechanisms that subserve the monkey's ability to detect innocuous cutaneous stimuli (air puffs) delivered to the face. The magnitude of sensations produced by small increases in air puff stimuli was studied by the use of a reaction time paradigm. The monkey initiated a trial by pressing an illuminated button. Subsequently air puff stimuli (AP1) of identical intensity were delivered to the face at the rate of one per second. After a variable time period between 4 and 10 seconds, a larger air puff (AP2) was presented. The subject was required to release the button as soon as the larger air puff stimulus was detected. Detection latency was defined as the time interval between the onset of the large air puff and the release of the button. Human subjects were trained in a similar paradigm except that they were not reinforced with cherry juice for correct responses. Both the monkey's and human's detection latencies to stimuli presented on the face were dependent on the intensity of the AP2. The psychophysical functions obtained from the monkeys face were monotonically related to the intensity of AP2. As the intensity of AP2 increased, the monkey's detections latencies became shorter. The humans' detection latencies to AP2 stimuli were also monotonically related to the intensity of the air puff. The psychophysical functions obtained form the humans' face were equivelent to those obtained from the monkey face. The monkey's and human's reaction time to air puff stimuli appear to be an accurate measure of the perceived intensity of innocuous cutaneous stimulation.